Copper plating composition and process



United States Patent F This invention relates to the electrodeposition of copper from aqueous solutions of its salts and is particularly directed to acid copper plating baths of greatly improved throwing power and covering power whereby uniformly distributed deposits of copper can be obtained over irregular shaped cathode surfaces.

Acid copper plating baths have practically no throwing power and cover very poorly in low current density areas of the cathode While having a tendency to produce coarsely crystalline or burnt deposits of a spongy substance in the high current density areas.

I have now found an addition agent for acid copper plating baths that greatly improves their throwing power and covering power thus enabling acid baths to approach cyanide copper baths with respect to these properties, cyanide copper baths being among the best in throwing and covering power properties.

My new addition agent for acid copper baths is chemically designated as para vinyl benzene sulfonic acid. It is not a brightener when used alone, but may be used with known brighteners if desired. Its sole fiunction is to greatly improve the covering power and throwing power of the acid copper bath. The concentration is not critical, about 0.3 gram per liter being optimum, with some efiect being noted at lower concentrations around 0.1 gram per liter. The upper concentration limit is not critical, but there appears to be no point in going above about 1 gram per liter, although more is not harmful. This compound is compatible with the usual ingredients of acid copper plating baths including the addition agents conventionally used in such baths.

Para vinyl benzene sul fonic acid is effective to improve throwing and covering powers in all of the acid copper plating baths in general commercial use, formulas for which can be found in Modern Electroplating and other standard reference works. Para vinyl benzene sultonic acid can be introduced into acid copper plating baths as an addition agent in any convenient form such as one of its bath soluble salts, for example, providing the anion is not harmful to the bath. As a matter of convenience I prefer to use the sodium salt, or para vinyl benzene sodium sulfonate.

As specific examples of-appl-ications of my invention I may cite the following formulations, while not in any way being bound by them.

3,109,784 Patented Nov. 5, 1963 Acid copper plating baths are operated at temperatures from about l20 F. and at current densities 'from about 20-50 amperes per square foot unagit-ated and at higher current densities, up to around 200 amperes per square foot or in some cases even higher with agitation, all of which is well known to those skilled in the art.

An addition agent for use in acid copper plating baths consists of an aqueous solution of the following approximate composition as an example:

Grams per liter Par-a vinyl benzene sulfonic acid (sodium salt) 15 Copper sulfate (CuSO .5I-I O) 10 This addition agent can then be added to acid copper plating baths in the proportion of about 15 cc. per liter or around 2 ounces per gallon of bath. It is obvious that the presence and identity of the copper salt is optional, and that the concentration of the para vinyl benzene sodium sulfonate can be raised to suit the purveyor by changing the propobtions in which it is added to the bath so as to produce a bath concentration of about 0.3 gram per liter, all within the scope of this invention.

Having thus described this invention in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains to make and use the same, and having set forth the best mode contemplated of carrying out this invention, I state that the subject matter which I regard as being my invention is particularly pointed out and distinctly claimed in what is claimed, it being understood that equivalents or modifications of, or substitw tions for, parts of the above specifically described embodiment of the invention may be made without departing from the scope of the invention as set forth in what is claimed.

What is claimed is:

1. In the process of electroplating copper from an aqueous acid solution of a copper salt, the step of adding to said solution between about 0.1 and about 1.0 gram per liter of para vinyl benzene sulfonic acid.

2. In the process of electroplating copper from an aqueous acid solution of a copper salt, the step of adding to said solution between about 0.1 and about. 1.0 gram per liter of para vinyl benzene sodium sulfonate.

3. A composition of matter for use in acid copper electroplating comprising water having dissolved therein, at room temperature, a copper salt and about. 0.3 gram per liter of para vinyl benzene sulfonic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,455,555 Brown Dec. 7, 1948 2,523,190 Brown Sept. 19, 1950 2,910,413 Strauss et al Oct. 27, 1959 FOREIGN PATENTS 1,141,135 France Mar. 11, 1957 OTHER REFERENCES Gray: Chem. Abstracts (1957), volume 51, C01. 15169bc. 

1. IN THE PROCESS OF ELECROPLATING COPPER FROM AN AQUEOUS ACID SOLUTION OF A COPPER SALT, THE STEPS OF ADDING TO SAID SOLUTION BETWEEN ABOUT 0.1 AND ABOUT 1.0 GRAM PER LITER OF PARA VINYL BENZENE SULFONIC ACID. 